Method and package for producing dental molds or molding material



Oct. 29, 1968 E, w, gw s ET AL 3,407,924

METHOD AND PACKAGE FOR PRODUCING DENTAL MOLDS OR MOLDING MATERIAL FiledJuly 18, 1966 2 Sheets-Sheet 1 INVENTORS E0701: W. Lewis Fa ler WardenJack {-1. Mill: Bernard F. MN/ck/a MD I A M,

BY Arronu'r Oct. 29, 1968 w, -;w s ET AL 3,407,924

METHOD AND PACKAGE FOR PRODUCING DENTAL MOLDS 0R MOLDING MATERIAL 1Filed July 18, 1966 2 Sheets-Sheet 2 Fig. 5

INVENTORS Euguu W. Lea/l: Fuller Warden Jack H. Mills Bernard R MM'ck/e"Tamil wwm United States Patent i O ABSTRACT ()F THE DISCLOSURE Apackage unit of a container having a gypsum powder material compressedand sealed therein and the methodof producing a liquid-gypsum mixtureused in dental application. 7

This application is-a continuation-in-part of our copending applicationSer. No. 530,196, filed Feb. 25, 1966, and entitled Method and Packagefor Producing Dental Molds or Molding Material. This invention relatesto improvements in the method and means for producing reproductions andmodels from dental molds, and more particularly, but not by way oflimitation, to a novel method and means for producing the moldingmaterial for making reproductions from dental impressions or molds, orthe like.

The most common method in use today for making models and reproductionsfrom dental impressions,v and the like, comprises the use of gypsummaterials which are mixed with water (or other suitable mixingadditives) in the desired proportions to obtain the desired consistencyfor the resultant molding material. This is usually accomplished bymixing the water with a quantity of the gypsum powder which is usuallymeasured from a bulk supply of the. gypsum material. The powdered gypsumis usually weighed and the Water measured to provide the desiredconsistency or the best results. However, as a practical matter the mostusual method in normal practice actually consists of placing a visuallyestimated amount of water in a rubber mixing bowl and manually dumping,or more preferably sifting an estimated quantity of the powder into thewater. This technique usually requires a secondary addition of eitherthe powder or the water to achieve an approximately correct consistencyfor the mixture. The ingredients are then mixed by manualstirringthereof with a spatula, or by a mechanical or motor driven spatulator,until a creamy mass results. As the mixture is being spatulated, themixing bowl or container is usually disposed in or held against avibrating mechanism or machine in order to agitate the mixture forrelease of as many air bubbles as possible therefrom.

The amount of air content normally present in bulk gypsum powders issubstantially great, and the materials produced by use thereof areusually exceedingly porous. Of course, the presence of air isundesirable in a material which is to be used for producing non-porousmodels, such as dental reproductions, and the like. In order to reducethe presence of airin the mixture produced by the above method, thematerial may be placed in a vacuuming machine for a time period ofapproximately forty-five seconds to one minute. However, since the sizeand cost of this vacuuming equipment is often excessive, very fewdentists, and only some of thedental laboratories are equipped with anyair removing devices.

The present method for producing the gypsum materials for dental models,and the like, as hereinbefore set forth, usually requires from one to.three minutes in spatulation, another minute of vacuuming, if vacuumed,and at least an additional minute in measuring the ingredients, and in.2 j the cleaning up of the mixing equipment and tools subsequent to themixing operation. Of course, after the mixture has been completed, thematerial is poured into an impression or mold, after which it sets up ina hard mass, as is well known.

The present invention contemplates a novel method and means forpreparing gypsum products for the making of models, reproductions, orthe like, from dental molds, or other related uses. The novel methodcomprises broadly the following steps: t

(1) Precompressionof a gypsum powder to decrease the volume and removesubstantially all the air I,

(2) Adding water tothe compressed powder in an accurate predeterminedquantity (3) Providing violent agitation of the powder and water toprovide'a superior end product.

The powdered gypsum product, such as plaster, hydrocal, investment, andthe like, is packaged within a suitable mixing container, which may bedisposable, and in an exact premeasured quantity. The powder is thencompressed in any suitable manner for removing air therefrom andreducing the volume thereof. The compressed powder is then sealed in thecontainer in such a manner that approximately 62 percent of the air isremoved and the volume of the powder is reduced by approximately 40percent. In the agitating operation or subsequent mixing procedureduring which the powder is mixed with water or any other suitableliquid, substantially all the remaining air is removed from theliquid-powder mixture so that the original powdered product occupiesonly approximately 36 percent of the original volume thereof, and theresultant liquidpowder mixture is substantially free of detrimental airvoids which cause failures in the surface of dental restorations.

The container in which the compressed powder is sealed is provided withan area or chamber separated from the powder and which is of avolumetric content substantially equal to the volume of water that isconsidered preferable for mixing with the preselected quantity of powderand which is to be mixed or added to the powder. The powdered productmay be packaged with only the compressed powder sealed within thecontainer or package and with a separate open or empty compartment beingprovided for receiving the mixing liquid at the time the material forthe reproduction process is to be mixed. Alternatively, the ingredientsfor the end product may be packaged in a single unit with thepremeasured compressed powder sealed in one compartment and thepremeasured quantity of the mixing liquid sealed in an adjacentcompartment, with a rupturable membrane, or the like, separating thecompartments whereby the liquid and. powder may be intermingled at thedesired time for producing the resultant material for the moldingoperation. In any event, the powder-liquid mixture may be violentlyagitated in any well known manner, and preferably by means of theagitating device disclosed herein whereby the mixture will be thoroughlymixed to provide an end product which is superior to that available withthe present methods, and to produce the end product in a minimum oftime. The novel method and means substantially eliminates any guess worksuch as now frequently employed in this type of mixing, and provides amixture based on the most desirable liquidpowder ratio.

When itis desired to use the package provided with both the powdered andliquid ingredients sealed therein, the membrane separating the twoelements is ruptured and the package containing both the liquid, orwater and the powder is vigorously agitated in-a mechanical mixer(similar-to that depicted herein) for a sufficient periodof time,generally approximately five seconds, to provide thorough 3 and adequatemixing of the powder and water. The rupturing of the diaphragm may beaccomplished in several different ways, for example, by the use of atear strip where the upper end of the cylinder or container is providedwith a removable cap with a cord connecting from thecap to the tearableportion of the diaphragm or membrane. Thus, at the time of intended usethe removable cap is removed, tearing the membrane. The torn portion isremoved from the cap and the cap is re-seated prior to the mixing step.Another way of providing a frangible diaphragm is to attach oneperipheral portion thereof to the one portion of a container and anotherperiphery portion to a portion of a separable container. Then, at thetime of intended use of the package, one container is rotated withrespect to the other container, and the membrane is torn. After themixing step is completed, the upper container portion may be removed anddiscarded, andthe lower container portion will contain or will be filledwith a properly proportioned and homogeneous mixture of powder andwater.

A When it is desired to use the package containing only the premeasuredcompressed powder sealed therein with the empty compartment separatedtherefrom, the liquid may be added to the empty compartment until thecompartment is completely filled or filled to the indicated marker. Theseal member may then be ruptured, or broken, in any well known manner,and the entire container may be disposed within agitating device,preferably the agitating mechanism depicted herein. The container isdisposed within the receiving portion of the agitator, and a cap memberis then secured on the receiving portion for sealing the containertherein. A slight air space is retained between the water level and thecap member to provide a mixing area. The container is then violentlyagitated and the powder and water are thoroughly mixed to provide aresultant homogeneous mixture which is of the proper proportions, andwhich is substantially free of air voids. It is an important object ofthis invention to provide a novel method for producing a gypsumaliquidmaterial for models and reproductions from dental molds, and the like,in a manner wherein air voids are substantially eliminated :from theresultant gypsum-liquid mixture.

It is another object of this invention to provide a novel method ofpackaging a gypsum product in powdered fOIIIl whereby the powder isprovided in premeasured quantities for facilitating the production of aliquid-gypsum end product.

Another object of this invention is to provide a novel method ofpackaging a premeasured quantity of a powdered gypsum product which isprecompressed for removal of air and reduction of volume of the powderto produce a superior end product substantially free of air voids.

Still another object Oif this invention is to provide a novel means forfacilitating the mixing of a premeasured quantity of powdered gypsum anda premeasured quantity of liquid to provide a homogeneous end productwhich is substantially free of air voids.

It is a further object of this invention to provide a novel package inwhich both of the powdered and liquid ingredients for a dental modelmaterial are contained within the package.

It is still a further object of this invention to provide a novelpackage in which only the premeasured and precompressed poweredingredient of a dental model material is sealed therein with a separatechamber being providedfor receiving a predetermined quantity of liquidtherein.

' 'A still further object of this invention is to provide a novelpackagewhich serves as the mixing container for the dental model material.

Another object of this invention is to provide a novel method and meansin which the powder and water ingredients of a dental model material, 01the li can b 4 joined together in a quick and easy fashion when readyfor use.

Still another object Otf this invention is to provide a novel method andmeans for providing the powder and water ingredients of a dental modelmaterial, or the like, in their exact proportions, weights and volumes.

It is another object of this invention to provide a novel package, theingredients of which may be thoroughly mixed in a closed system withoutthe incorporation of additional air. 1

Another object of this invention is to provide a novel package forpowdered and liquid ingredients which is disposable.

It is also an object of this invention to provide a unique and novelmethod and means for producing a model material for dental operationswhereby the end product is accomplished through controlled and automaticaccuracy by means of the novel mixing and packaging method.

Other and further objects and advantageous features of the presentinvention will hereinafter more fully appear in connection with adetailed description of the drawing in which:

FIGURE 1 is a sectional elevational view of a container embodying theinvention.

FIGURE 2 is a sectional elevational view of a container embodying amodification of the invention.

FIGURE 3 is a front elevational view of an agitator apparatus embodyingthe invention.

FIGURE 4 is a view taken on line 44 of FIGURE 3.

FIGURE 5 is a view taken on line 55 of FIGURE 3.

FIGURE 6 is a sectional view of the container and receptacle of theagitator apparatus.

Referring to the drawings in detail, and particularly FIGURE 1, acontainer 10 is provided for receiving a suitable precompressed gypsumpowder 12 in the lower portion thereof. The container 10 may beconstructed from any suitable material, however it is preferable thatthe container 10 be constructed from a disposable plastic material ofsufficient rigidity to withstand the agitation operation, as will behereinafter set forth, and of a light weight construction. The container10 as depicted in FIG- URE 1 is preferably of a substantially conicalconfiguration generally similar to the well known Dixie Cup widely usedfor cold drinks, and thelike. It will be apparent, however, that theconfiguration of the cup or container 10 may be of any dasired shape. Anoutwardly extending circumferential flange 14 is provided around theupper open end -16 of the container 10 for a purpose as will be behereinafter set forth.

The quantity of powder 12 is premeasured prior to insertion thereon intothe container in order to provide substantially the exact amount thereofrequired for producing the optimum end product. The premeasured powder12 is then compressed in any well known manner (not shown) and sealedwithin the lower portion of the container'10 by means of a suitablesealing member '18 whereby substantially 62 percent of the air isremoved from the powder 12 and the volume of the powder is reduced byapproximately 40 percent. The sealing member 18 separates the lowerportion of the container which contains the powder from the upperportion thereof whereby an empty chamber 20 is provided in the container10. The volume of the chamber 20 is preferably substantially exactlyequal to the volume of the liquid 22 (FIGURE 6) to be added to thepowder -12 to produce the desired end product. Thus, the chamber 20 maybe readily completely filled with the liquid 22 to provide thepremeasured quantity thereof for the optimum ratio with regard to thequantity of the powder 12; Of course, alternatively, a suitablemeasuring line or indication means (not shown) may be provided on theinner periphery of the chamber 20 to indicate the level for fillingthereof with the water, or other liquid additive.

The seal member 18 may 'be of any suitable type, and

may be removably disposed within, the container in any well known mannerwhereby the seal 18 may be removed immediately subsequent to theaddition of the water in the chamber 20. For example, the seal member-18 may be provided with a tab or pull member (not shown), or the like,which may be grasped manually for lifting the seal 18 from its positionwithin the cup or container. As an alternate means of sealing the powder12 within the container 10, it may be desirable to superimpose or stacka plurality of the containers 10 for storage purposes. In this event,each container 10 may be provided with an inwardly directed annularflange or rib member (not shown) spaced therein at the height ordistance from the bottom 24 of the container to define a chamber forreceiving the compressed powder 12. The bottom 24 of the next succeedingcontainer -10 may then be pressed or snapped into an engagement with therib member to seal the powder in the lowermost container 10. As one ofthe containers 10 is to be utilized for mixing of the liquid-powderproducts, the lowermost container 10 may be removed from the engagementwith the container stacked or superimposed thereon for breaking the sealof the powder and permitting addition of the water or other liquidadditive to the removed container 10.

Subsequent to the addition of the water in the chamber 20, thewater-powder mixture may be violently agitated in any desired manner toprovide a thorough mixing thereof. It is deemed preferable to utilizethe agitator apparatus generally indicated at in FIGURES 3 through 6.

The agitator device 30 comprises a motor 32 mounted on a base plate 34,or the like. The motor 32 may be of any suitable type, but it ispreferable to utilize a motor having an output of 1750 r.p.m. to achievethe desired results of agitation, as will be hereinafter set forth. Themotor 32 is provided with the usual output shaft 36 having a wheel 38secured to the outer end thereof for rotation simultaneously therewith.A peg or pin member 40 is secured to the outer face of the wheel 38 inany well known manner and extends axially outwardly therefrom, with theaxis of the pin 40 being substantially parallel with and spaced from theaxis of the output shaft 36. Of course, the distance between the axis ofthe pin 40 and shaft 36 may be of substantially any desired length, butas a practical matter it has been found that a distance of one halfinch, in combination with the 1750 rpm. output of the motor 32 providesa very efficient agitation operation. The pin member 40 extends throughan elongated aperture 42 provided in the proximity of one end of apivotal arm member 44. A suitable bearing member 46 is provided in theproximity of the outer end of the pin 40 for riding in the slot 42during the pivotal movement of the arm 44 as will be hereinafter setforth.

The opposite end 48 of the arm 44 is pivotally secured at 50 to a pairof spaced upright post members 52 and 54. A receptacle member 56 isinterposed between the pivot 50 and slot 42 and may be either suitablysecured to the arm 44 or may be integral therewith. The receptacle 56 isprovided for reciving thecontainer 10, and is preferably of aconfiguration generally similar thereto, as particularly shown in FIGURE6.

The receptacle 56 is provided with an internal chamber 58 of a generallyconical configuration corresponding to the outer configuration of thecontainer 10 for receiving the container 10 therein. The lower wall orbottom 60 of the receptacle portion 56 is provided with an aperture 62for facilitating removal of the container 10 from the chamber 58subsequent to the agitation operation. An annular shoulder 62 isprovided on the inner periphery of the chamber 58 in the proximity ofthe upper end thereof for receivingthe flange 14 thereagainst. Anupwardly extending circular flange 64 is provided at the upper end ofthe receptacle 56 and is internally threaded at 66 for receiving asuitable threaded cap 1member-68 therein. A mixing area 70 is providedbetween the upper level of the container 10 and the lower internalsurface of the cap 68 for facilitating the mixing of the liquid 22 andpowder 12 during the agitation operation.

Of course, it will be apparent that a second receptacle member (notshown) may also be provided on the arm 44, and may be either carried atthe outer extremity of the arm beyond the pin member 40, or disposedbetween the pivot 50 and pin 40. The second (or other) receptacles maybe either of substantiallythe same size as the receptacle 56, or ofeither larger or smaller sizes in order to receive containers 10 ofvarying sizes for agitation thereof. In addition, it may be desirable toprovide a suitable adaptor member (not shown) for insertion within thechamber 58 of the receptacle 56 for adapting the size of the chamber 58for substantially any size container 10. Of course, the adaptor membermay be of a generally similar configuration as the chamber 58 andcontainer 10, or any other desired shape as practical. When it isdesired to provide a gypsum-liquid material for making a model orreproduction from a dental mold, orthe like, one of the containers 10may be selected which is prepacked with the desired quantity of powder12 in accordance with the desired end product. The premeasuredprecompressed powder 12 is sealed within the container 10, ashereinbefore set forth, and when it is desired to produce thewater-powder mixture, the seal member 18 may be removed from thecontainer 10 in any well known manner, and the chamber or area 20 abovethe powder 12 may be filled to the brim (or to the filling indicatorline) with the water, or other liquid, to be added to the powder. Thecontainer 10 thus filled with the water and powder ingredients may thenbe disposed within the chamber 58 of the receptacle 56 as shown inFIGURE 6. The cap member 68 is then threadedly secured on the receptacle56 whereby the cap 68 engages the lip or flange 14 of the container 10to secure the container within the chamber 58 and to provide a sealthere-between in order to preclude leakage of the mixture during theagitation operation. The motor 32 may then be activated in the usualmanner whereby the shaft 36 is rotated for rotating the pin 40 in acircular path about the axis of the shaft 36. The engagement between thebearing 46 and slot 42 causes the arm 44 to oscillate very rapidly aboutthe pivot 50 whereby the receptacle 56 and container 10 therein areviolently agitated. The area 70 above the liquid level provides a mixingarea, and the powder and liquid are thoroughly mixed after approximatelyfive seconds of agitation.

The motor 32 may then be stopped, and the cap 68 may be removed topermit access to the container 10. The container 10 may be removed fromthe chamber 58 by manual upward pressure on the bottom 24 through theaperture 62. The container 10 will contain a thoroughly mixed orhomogeneous mixture which is substantially free of air voids. Of course.the container 10 may be discarded. if desired, subsequent to removal ofthe waterpowder mixture therefrom, thus eliminating or greatly reducingthe clean-up operation after the mixing of the material.

Referring now to FIGURE 2, a modified form of the invention is depictedtherein which comprises a container 70 including a lower generallycylindrical member 72 for receiving a premeasured quantity ofprecompressed powder 74, and an upper substantially cylindrical member76. The cylindrical members 72 and 76 may be constructed of any suitablematerial; for example the cylinder 72may be of a metallic construction,and the cylinder 76 may be of a plastic construction; or both cylinders72 and 76 may be constructed from a suitable plastic material wherebythe entire container 70 may be disposable. The lower end of thecylindrical member 72 is sealed or closed by a disc member 78, which maybe of plastic material. A rupturable diaphragm or membrane 80 is sealedagainst the upper end of the cylinder 72 after 7 the cylinder 72 hasbeen filled with the compacted powder 74 as will be hereinafter setforth.

The upper end of the cylindrical member 76 is pr vided for retaining asupply of liquid 81 which corresponds in quantity with the mostdesirable ratio of water to the powder 74 contained within the cylinder72. The upper end of the cylinder 76 may be closed in any suitablemanner after the addition of the liquid, such as by a dome shaped member82 which may be bonded to the cylinder 76 in a manner that the twopieces become integral. The upper end of the cylinder 72 is providedwith an outwardly extending lip 84 and the lower end of the cylinder 76is provided with an inwardly directed lip 86 which cooperates with thelip 84 to provide a fluid tight seal when the member 76 is telescopedover the lower member 72. An outwardly projecting shoulder 88 isprovided on the cylindrical member 72 as a stop to prevent furtherdownward movement of the member 76 beyond that shown in FIGURE 2. Theshape of the lips 84 and 86 are (and indeed their presence) is notcritical as far as the present invention is concerned just so long asthe upper member 76 is adapted to fit snugly against the top of thelower cylindrical member 72 as shown in the drawings.

The diaphragm 80 resting against the top of the cylindrical member 72extends downwardly between the intermating portions of the members 72and 76 and extends somewhat outwardly as at 90.

Prior to filling the lower cylinder 72 with the powdered product 74 itmay be desirable to cover the inside surface with a thin layer 92 ofasbestos material to compensate for expansion of the powder and also toprovide a path of escape for any gases that are generated during theheating and casting operation; to the extent that the strip 92 might beconsidered as a spacer for expansion of the powder, the use of thisasbestos sheeting may be eliminated because the member 72, being of athin and disposable nature, may allow for adequate expansion by itself.

A quantity of the powder 74 is compacted into the interior of thecylindrical member 72 by compression; if the compression forces aresufliciently complete and/or uniform the amount of powder 74 containedwithin the cylinder 72 will be the same in each case because theinternal volume of the cylinder 72 will be constant. However, thecylinder 72 can be weighed before and after filling with the powder 74to insure an accurate quantity of powder therein. Heretofore attemptshave been made to eliminate the air from the powder mix by means ofagitating and/or vacuuming by the utilization of machines designed forthese purposes. However, it has been discovered that either or both ofthe expedients have been largely unsuccessful in removlng the air fromthe powder as desired. The powder itself can be purchased in bulk formor in pre-weighed package generally containing about 50 grams. These 50grams generally occupy about 55 cc. of volume. By using mechanicalcompression on the powder it has been discovered that a 50 gram sample,which would normally occupy approximately 50 cc. of volume, can becompressed to about 30 cc. of volume which means that about cc. of airhas been removed.

After the cylinder 72 has been filled with compacted powder 74, thediaphragm 80 is placed over the top and held in position while themember 72 is inverted from the upright position shown in FIGURE 2. Anyconvenient meanscan be employed to hold the membrane 80 in this positionduring the assembly. At this point a quantity of adhesive material (notshown) is applied to the outer surface of the lip 84 and extendstherearound for approximately 180. At the same time a second quantity ofadhesive material is placed on the inside of the member 76 generallyinwardly of the lip 86 and also extends therearound for approximately180. When considering the ultimate juncture the 180 portion of adhesiveon the lip 84 -is oppositely disposed from the 180 portion of adhesiveon the lip 86. Thereafter, the cylinder 76 is urged downwardly and overthe upper end of the lower cylinder 72, forcing the diaphragm againstthe lip 84 and at the same time against the inside of the container 76.Thus, the membrane 80 adheres to the adhesive portion on the lip 84 andto the adhesive portion on the lip 86. It must be noted now that oneportion of the diaphragm 80 is connected adhesively to the lowercontainer 72 and another portion is adhesively connected to the uppercylinder 76. During the aforementioned assembly, it is preferable thatthe bottom portion of the container 76 should be compressed slightly soas to reduce the volume thereof in order to compenaste for thecompression resulting from the com bination of the two members. Afterthe assembly has been completed, however, and the pressure is releasedfrom against the bottom of the member 76, it can return to its originalvolume and thus the compressive force is fully compensated. Naturally,if the assembly takes place in an evacuated or partially evacuated area,no concern need be given to any deliberate squeezing of the outer end ofthe member 76.

After the upper cylinder 76 has been assembled with the lower cylinder72, the premeasured volume of quantity of liquid 81 may be placed orinserted into the upper cylinder 76. The cover or dome shaped member 82may then be placed on top of the cylinder 76 and cemented in position,or bonded thereto to provide a sealed package for the water and powderingredients. A mixing area or air space 94 is provided between the upperlevel of the water (or other liquid additive) 81 to permit mixing of thewater and powder ingredients.

When it is desired to produce a material for a dental reproduction, orthe like, the upper cylinder 76 may be manually rotated or twistedslightly with respect to the lower cylinder 72 for causing a rupturingof the diaphragm 80, thereby joining the ingredients within thecontainer 70 without violating the closed container systern. The entiresealed container 70 may then be disposed in an agitating device similarto that depicted in FIG- URES 3 through 6 whereby the water and powderwill be thoroughly mixed to produce a superior homogeneous mixture whichis substantially free of air voids. Of course, any other suitable meansof agitation may be utilized for the mixing of the ingredients.

Subsequent to the agitation operation, the upper cylinder 76 may beremoved from the engagement with the lower cylinder 72 and the mixturewill be contained within the lower cylinder 72. The material thusproduced may then be utilized in the usual manner for making areproduction of a dental impression, or the like, bearing in mind thatthe product is superior than that possible with the present day methods.In addition, both the cylinders 76 and 72 may be discarded after use,which eliminates or greatly reduces the clean up operation after theproduction of the water-powder material.

From the foregoing it will be apparent that many of the steps of theprior art have been eliminated. For example, there is no need to mix thepowdered product separately and as a result there is no need to clean aseparate vessel or any of the implements necessary for the mixingoperation. There is no need to attempt to apply a vacuum to remove airfrom the powder because this has already been accomplished by thecompacting process. The container of the pre-measured ingredients may bediscarded subsequent to the production of the end product thuseliminating or substantially reducing the clean up operation. Withregard to the materials which may be provided in the packages and methodof the present invention, it will be apparent that any other materialhaving the same characteristics as the gypsum powder and water may beutilized and it is recognized that the dentistry profession utilizesmany molds which are prepared from a powder-liquid mixture. These wouldinclude the various plaster, stones, acrylics, alginates, or the like.The method and means of the present invention may be utilized forproviding the dentist or the dental technician preweighed andpreportioned quantities of powder and liquid for any one of severalmolding mixtures to produce a superior resultant end product which is ofa homogeneous mixture and substantially free from air voids.

Changes may be made in the combination and arrangement of parts asheretofore set forth in the specification and shown in the drawings, itbeing understood that any modification in the precise embodiment of theinvention may be made within the scope of the following claims, withoutdeparting from the spirit of the invention.

What is claimed is:

1. A method of providing powdered gypsum for a re sultant liquid-gypsummixture for dental applications which consists of placing a premeasuredquantity of the gypsum in a container, removing substantially all theair from the gypsum whereby said resultant liquid-gypsum mixture will besubstantially free of air voids, and sealing the premeasuredsubstantially airless gypsum in a portion of the container.

2. A method of providing a powdered gypsum for a resultant liquid-gypsummixture for dental applications as set forth in claim ll wherein an areais provided adjacent to but separate from the sealed gypsum forreceiving a premeasured quantity of the liquid.

3. A method of producing a liquid-gypsum mixture for dental applicationswhich consists of an initial step of removing substantially all the airfrom the gypsum, add ing the liquid to the gypsum subsequent to theremoval of the air therefrom, and mixing the liquid with the gypsum toremove substantially all the remaining air and to provide a homogeneousmixture which is substantially free of air voids.

4. A method of producing a liquid-gypsum mixture as set forth in claim 3wherein the gypsum is premeasured prior to the removal of the airtherefrom, and the quantity of liquid is premeasured in proportion tothe quantity of the gypsum.

5. A method of producing a liquid-gypsum mixture as set forth in claim 3wherein the substantially airless gypsum is sealed in a container.

6. A method of producing a liquid-gypsum mixture as set forth in claim 5wherein an area of predetermined volume is provided for receivingsubstantially the exact quantity of liquid in proportion to the gypsumsealed in the container.

7. A packaged unit for a liquid-gypsum mixture for dental applicationswhich comprises a container, a premeasured quantity of gypsum sealed inone portion of the container, said gypsum having substantially all theair removed therefrom prior to the sealing thereof in the container, achamber provided in the container for receiving a liquid therein wherebythe liquid and gypsum may be mixed within said container to provide ahomogeneous mixture which is substantially free of air voids.

8. A packaged unit for a liquid-gypsum mixture for dental applicationsas set forth in claim 7 wherein the substantially airless gypsum is of apremeasured quantity,

and the liquid receiving chamber is of a preselected volume forreceiving substantially exactly the proper quantity of liquid inproportion to the gypsum.

9. A packaged unit for a liquid-gypsum mixture for dental applicationsat set forth in claim '7 wherein a seal member is disposed within thecontainer for sealing the gypsum therein, said seal member being movableupon the application of force whereby the liquid and gypsum ingredientsmay be admixed to provide a resultant liquidgypsum mixture which issubstantially free from air voids.

10. A packaged unit for a liquid-gypsum mixture for dental applicationsas set forth in claim 7 wherein the liquid receiving chamber is sealedsubsequent to the addition of the liquid therein in order that theentire container may be utilized for mixing the liquid and gypsum toprovide said homogeneous mixture which is substantially free of airvoids.

11. A package unit for facilitating the production of a liquid-gypsummixture for dental applications which comprises a container, apremeasured quantity of gypsum disposed in the lower portion of thecontainer, said gypsum having substantially all the air removedtherefrom, a movable seal member disposed in the container adjacent theupper level of the gypsum for sealing the substantially airless gypsumwithin the container, and a liquid receiving chamber provided in thecontainer adjacent the seal member and separated from the gypsum by theseal member whereby the liquid and gypsum cannot be inadvertently mixed.

12. A package unit for facilitating the production of a liquid-gypsummixture for dental application as set forth in claim 11 wherein theliquid receiving chamber is of a preselected volume for retainingsubstantially the exact quantity of liquid in proportion to the quantityof the gypsum sealed within the container.

13. A method of providing a powdered gypsum for a resultantliquid-gypsum mixture which consists of placing a premeasured quantityof gypsum in a container, removing substantially all the air from thegypsum, sealing the premeasured substantially airless gypsum in aportion of the container, providing an area of preselected volumeadjacent to but separate from the sealed gypsum for receiving andautomatically measuring a quantity of liquid to provide the desiredliquid-gypsum ratio.

References Cited UNITED STATES PATENTS 1,770,118 7/1930 Williams .a206-47 1,889,111 11/1932 Serr 20647 2,759,712 8/1956 Hvistendahl 259722,959,900 11/1960 Wollett 53-24 3,056,244 10/1962 Bartels 53-243,128,082 4/1964 Cline 259-72 WILLIAM T. DIXSON, JR, Primary Examiner.

